HarmonyOS 如何实现APP切到后台以及在后台查看时蒙层遮罩效果

参考如下代码：

在EntryAbility中onWindowStageCreate方法中添加AppStorage.setOrCreate(‘windowStage’,windowStage);

page中demo如下：

import { window } from '@kit.ArkUI';

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';
  @State flag: boolean = false
  onPageShow(): void {
    let windowStage = AppStorage.get("windowStage") as window.WindowStage;
    windowStage.on("windowStageEvent", (data) => {
      if (data === window.WindowStageEventType.PAUSED) {
        this.flag = true
      }
      else {
        this.flag = false
      }
    })
  }

  build() {
    Row() {
      Column() {
        Text(this.message)
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
      }
      .width('100%')
    }
    .height('100%')
    .foregroundBlurStyle(this.flag ? BlurStyle.Thin : BlurStyle.NONE, {
      colorMode: ThemeColorMode.LIGHT,
      adaptiveColor: AdaptiveColor.DEFAULT
    })
  }
}